I'm late to the party--here's Chris Stedman saying yes, here's Josh Rosenau strengthening the case and Joe Hoffman saying maybe not, while others hate the whole idea (see the Stedman post for details).
The idea that atheists could be involved in interfaith work dawned on me a couple of years ago when I attended an interfaith panel on the crisis in Darfur. [Now I remember ... I wrote about this before!] The panel included a rabbi, a college chaplain and an imam. I was there as chair of a large Darfur initiative at the rabbi's synagogue. I found myself looking at things through two sets of eyes. I was proud of the rabbi. He had visited Darfuri refugee camps himself, and our initiative was nationally supported and very effective at raising money and awareness (Nicholas Kristof mentioned it in a 2005 column). On the other hand, it seemed to me the panel should have included someone with a non-theistic perspective. This couldn't just be an ethicist, or foreign affairs expert, or what not--this was a panel assembled to represent diverse religious perspectives. But why not an atheist or a secular humanist?
Some atheists really don't like the idea. The main objection seems to be that if atheists get involved with "inter-faith" work, that will send the message that atheism is based on faith. That, I think, is a superficial objection. In fact, religious people could have the same worry. Many believers believe because they think they have a sound argument to support their belief-- they don't believe "on faith." So "faith" is already being used loosely here. An inter-faith panel is really just a panel composed of members of different religious communities--faith, schmaith. So the real question is: are atheists members of religious communities?
Some are, some aren't. Just being an atheist doesn't really make you a member of such a community. But some atheists do organize themselves into groups in a religion-like way. In fact, I spoke at such a group on a recent Sunday morning. There was inspiring music, there were nice, warm messages, but it was all 100% godless. (And then there was my dark little talk about whether people ought to exist...!) I can easily imagine someone leading a "freethinker" initiative on Darfur, and thus having a basis for being included on that panel alongside the rabbi, the chaplain, and the imam.
What's left, then, as an objection to atheists doing interfaith work? There's this--and for some, I think it's the main thing: being on such a panel forces people into a posture of mutual respect. A foaming-at-the-mouth anti-Jewish imam isn't going to be invited, nor is a rabbi who despises Christianity, or a Christian who's constantly voicing contempt for non-Christians. To get on a panel like this, a freethinker has got to reject religious belief nicely, in just the "I respect you, but..." way that Jews, Christians, and Muslims disagree with each other. To the extent that the most visible sort of atheism today is less respectful than that, the interfaith-suitable freethinker is going to have to be different. And overtly different too--they're going to have to reassure religious leaders that they are "like this, not like that." That's the price of inclusion--and I think inclusion on that Darfur panel would have been desirable.